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Category: Reliability Testing

How to Make Your Product More Reliable Through Testing

At DES, we have tested many different kinds of products ranging from medical devices to aerospace products.  We have performed numerous reliability tests and developed numerous accelerated life test plans.  Many times, our customers ask us, “How do we make our products more reliable?”  There are analytical methods and processes that can be used to improve product reliability.  However, the focus of this article will be How To Make Your Product More Reliable Through Testing. 

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MIL-STD-810 Vibration Testing Overview

This is part one of a series of blog posts discussing MIL-STD 810 Vibration Testing.  This blog was written with reference to MIL-STD-810G w/Change 1 dated 15 April 2014.  DES has the experience and expertise to help you determine what profiles are appropriate for your product and to run your MIL-STD-810 vibration test.  Check out our vibration testing capabilities here.

MIL-STD-810 is a public military test standard that is designed to assist in the environmental engineering considerations for product design and testing.  For the purposes of this blog series we will focus on Method 514.7, titled Vibration.  This section defines the environmental vibration conditions a material or product may experience during the product life cycle and translates these conditions into replicable test procedures.  Unfortunately, unless you’re familiar with this document, this section or any section for that matter may seem a little daunting.  This blog will hopefully provide some guidance into navigating your way through it.

vibration testing standard MIL-STD-810
Figure 1. Table 514.7-I from MIL-STD-810G w/ Change 1

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Door Open/Close Accelerated Life Test Case Study

Customer Goal

A customer contacted DES, seeking to create a reliability test plan for their product based on customer usage, new features and design limits.  One of the concerns identified by the customer was the need for an accelerated life test which tested whether their “door assembly” product met the design specification for usage.  In other words, the goal was to create an automated test solution which opened and closed cabinet doors to the estimated amount they would see during a lifetime in the field.

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Circuit Board HALT Testing Case Study

HALT Test Setup on Circuit Boards
HALT Test Setup on Circuit Boards

Customer Goal

A customer approached DES looking to perform Highly Accelerated Life Testing (HALT) on a new circuit board design.  DES and the customer agreed to test the circuit boards using DES’s traditional HALT test procedure which calls for hot/cold temperature steps followed by rapid temperature ramping, vibration steps and combined temperature and vibration stresses.  HALT testing on electrical componentry is quite common across industry to expose design weaknesses; both mechanical and electrical (What is HALT and Why Perform HALT?).  Typical failures include poor solder connections, overheating, component failure, etc. (What Kind Of Failures Occur During HALT?)

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Cooling Fan Reliability Testing Case Study

Fan Reliability Testing Case StudyCustomer Challenge

A customer approached DES looking to find an accelerated test solution for an AC powered cooling fan used in one of their products.  The product had been established in the marketplace and the company was now looking for ways to reduce cost by looking at different cooling fan suppliers.  Most fans, however, have a mean life rated for over 20,000 hours, so a typical accelerated life test would require a significant amount of time and money. 

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Choosing A Vibration Test Lab Part 2

Part 2 – Selecting a Lab and Performing Your Test

If you have not done so yet, please check out Part 1 – Defining your project and  Obtaining a Quote.

You obtained quotes from a couple of vibration test labs.  Your next task is to select a vibration test lab to perform your vibration test.  Your selection should not be based upon price alone.  Factors that should affect which lab you choose are capability, cost, timing, location, quality, and other special requirements.

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Choosing A Vibration Test Lab Part 1

Part 1 – Defining your project and Obtaining a QuoteVibration Test Equipment

Vibration testing is a very specialized field, not very well understood by many.  There are different types of vibration and there are an enormous number of vibration test specifications.  Vibration testing equipment is very expensive to purchase forcing many companies to hire a vibration test lab to fulfill their vibration testing requirements.  So what should you expect when Choosing A Vibration Test Lab?

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Mixed Mode: Sine on Random Vibration Testing, RoR, SoRoR

random vibration testing

Mixed Mode Vibration Testing is less common than Sinusoidal and Random Vibration Testing.  However, it does have a special purpose for simulating specialized helicopter vibration or vibration from tracked vehicles such as tanks.

The three mixed modes of vibration testing are:

  • Sine-on-Random (SoR)
  • Random-on-Random (RoR)
  • Sine-on-Random-on-Random (SoRoR)

Some common test standards that have specifications for Mixed Mode Vibration Testing are:

  • MIL-STD-810 Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests
  • RTCA DO-160 Environmental Conditions and Test Procedures for Airborne Equipment

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What Kind Of Failures Occur During HALT?

Product failures in HALT testing are defined as either the cessation of any functions or an out-of-specification condition for any performance characteristic. When a failure occurs, it is documented in DES’s HALT log. The exact time and test condition when each failure occurred is noted.

If the product fails to operate, the temperature or vibration will be changed toward ambient room conditions followed by a short dwell period to see if the product recovers. If the product is non-operational after dwelling at ambient conditions, trouble shooting will take place to find the failed component. The failed component will then be removed, repaired or replaced with a new component (as is practical) in an effort to expand the test stresses.

Relevant Failures

Figure 1 - Failure of Improperly Designed Mounting Tabs
Figure 1 – Failure of Improperly Designed Mounting Tabs

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What Equipment Is Used For HALT?

HALT Chambers

Figure 1 - DES’s HALT Chambers
Figure 1 – DES’s HALT Chambers

Specialized test chambers are needed to perform a HALT. Typical HALT chambers are shown in Figure 1. The specification for HALT chambers is typically the following:

Liquid nitrogen (LN2) is used to cool the air temperature in HALT chambers. This allows for very rapid temperature changes of 60°C per minute and a cold temperature extreme of -100°C.

HALT chamber heating is provided by high power resistive heating elements that can produce changes of 60°C per minute and a hot temperature limit of +200°C.

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